As far as I can guess from the sources:
The base system is based on a Gumstix board.
The CPU is XScale PXA250.
The I/O chip to talk to the PN-LCD, keyboard, scrollwheel and battery is from Foxconn.
Flash chip is OneNAND from Samsung.
The CDMA modem is AnyData DTG.
USB controller is Philips ISP1761 (it has On-The-Go!).
Eink controller is Apollo (the older one used in PRS-500 etc, I think).
Audio is WM8971.

I downloaded the source code, but there's a fair amount of stuff missing before you can start compiling...

I made the mistake of upgrading to 2.0.3 and then realised I couldn't do USB tethering anymore ...
I'd like to downgrade, or better compile my own firmware. I'm quite familiar with the ARM architecture